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Ex-smokers 'pile on the pounds'

Wednesday 11 July 2012

“The average weight gain associated with giving up smoking is much higher than previously thought,” BBC News has reported.

The story comes from a study looking at weight change in smokers who managed to quit the habit for up to 12 months, without receiving drug treatment. It found that giving up smoking was associated with an average increase in body weight of 4-5kg (9-11lb), a year after quitting.

Weight gain is common in people who have given up smoking because nicotine acts as an appetite suppressant. This means that the quitters may find themselves eating more. The results of this research are surprising as the average weight gain is higher than the expected weight gain of around 3kg. However, on a more positive note, the researchers also found that one-in-six people studied actually lost weight after quitting smoking.

The authors of the research speculated that a possible limitation to the study may be that people who need to seek help to quit smoking may also have difficulties in avoiding weight gain after smoking (possibly due to factors such as reduced willpower or similar). So the finding may not necessarily be the same in people who successfully quit smoking without seeking treatment. But there is no hard evidence to support this speculation.

The weight gain that occurs after quitting does not have to be permanent and can be lost using a combination of a calorie-controlled diet and exercise.

For most people, the health benefits of giving up smoking far outweigh any modest temporary change in weight. While ex-smokers may have to invest in new trousers or dresses, this is a small price to pay for their massively reduced risk of developing potentially fatal diseases such as lung cancer.

Where did the story come from?

The study was carried out by researchers from Paris-Sud University, Emile Roux Hospital and the University of Birmingham. There was no special funding for the research but the UK team was funded by the UK Centre for Tobacco Control Studies. The study was published in the peer-reviewed British Medical Journal.

The review was reported fairly, if uncritically, in the papers, with an emphasis on the average weight gain in quitters reported in the study. The BBC report included a comment from the Department of Health, while the Guardian included comments from an independent expert.

What kind of research was this?

The authors said that although giving up smoking results in considerable improvements in health, it is often accompanied by weight gain, since one of the most common side effects of nicotine withdrawal is increased appetite. However, previous estimates of the amount of weight gained by smokers who have quit has varied.

This was a meta-analysis that aimed to look at average weight change and variations in weight change in smokers who managed to quit the habit for up to 12 months, without using drug treatments to help them. While meta-analysis is useful for combining the findings from several studies to get a better view of the size of an effect, it does have drawbacks. The findings from meta-analyses depend on the different design and aims of the individual studies, and can be hampered by issues such as differences in the demographics of the populations being studied. This review included a variety of studies, which were broadly categorised as follows:

  • Most trials looked the effectiveness of smoking-cessation therapies for quitting.
  • Some trials looked at the effect of exercise to help quitting.
  • Some trials looked at the effect of interventions to prevent weight gain after quitting.

The authors were specifically interested in weight change among people who successfully gave up smoking and people who did not receive treatment to help them quit. For this reason, the focus of their report was on weight change in “untreated quitters”; in other words, the trial participants allocated to the “control” groups, who did not receive any treatment to help them quit.

What did the research involve?

The researchers had recently conducted a Cochrane systematic review of interventions to prevent weight gain after stopping smoking. For that review, they had searched through the reference lists of previously conducted reviews listed in the Cochrane Library that had looked at the effectiveness of smoking-cessation treatments. For the present review, the authors performed an updated search of the Cochrane CENTRAL register (Central Register of Controlled Trials) to identify additional trials that had been published since the last search date for each of those Cochrane reviews.

To be included in the present review, the studies had to have data available for weight change from “baseline” (the start of a study) to at least one follow-up point for people who had quit smoking.

Of the 212 trials identified that had looked at the effects of nicotine replacement therapy (NRT), exercise or other drug treatments for smoking cessation, only 54 of these recorded weight change at some point during follow-up. Of these, 51 were suitable for inclusion, because the remaining three included treatments that could have affected weight gain. These trials were used to estimate average weight change and variations in weight change in both quitters who did not have treatment (the data from the control arm of each trial) and those who were treated.

A further 11 trials were included that had looked at the effectiveness of specific treatments to prevent weight gain after smoking cessation. In these trials they looked at data from the control groups only, who did not have treatment. 

Although the focus of the study was on people who gave up smoking without any treatment, the researchers also examined the weight change for those who gave up with the support of a variety of treatments (NRT, other drug treatments or exercise).

The authors used established methods to assess the quality of included studies, and established statistical techniques to combine the results of these studies in meta-analysis.

What were the basic results?

From the 62 included studies, the researchers found that in people who quit smoking without any treatment, the average weight gain was 2.85kg (95% confidence interval 2.42 to 3.28) at three months and 4.67kg (95% confidence interval 3.96 to 5.38) at 12 months after quitting.

They calculated that at 12 months after cessation:

  • 16% of untreated quitters lost weight
  • 37% gained less than 5kg
  • 34% gained 5kg-10kg
  • 13% gained more than 10kg

Among the “treated” groups who quit smoking with the support of different drug treatments, estimates of weight gain were similar to the untreated quitters. Estimates were also similar between people especially concerned about weight gain and those who were not concerned.

How did the researchers interpret the results?

The researchers concluded that stopping smoking is associated with an average increase of 4kg-5kg in body weight after 12 months, with most weight gain occurring within three months of quitting. They pointed out that the variation in weight change is large, with about 16% of quitters losing weight and 13% gaining more than 10kg.

They argued that previous reports have underestimated the average amount of weight gained when people stop smoking. Gaining weight after smoking cessation, they said, limits some of the health benefits of quitting and is associated with an increased risk of health problems. They suggested that doctors “might usefully give patients who aim to give up a range of expected weight gain”.


Many people who want to give up smoking are concerned about weight gain and the media coverage of this study risks deterring them from trying to quit. However, this review had some important limitations that mean the findings should be viewed with some caution.

Variation between the included studies

This review included:

  • trials looking the effectiveness of smoking-cessation therapies for quitting
  • some trials looking at the effect of exercise to help quitting
  • some looking at the effect of interventions to prevent weight gain after quitting

Most of the trials included in the study (51 out of 62) looked at the effectiveness of different treatments to help smoking cessation, rather than weight gain. As weight gain was not the main outcome under investigation in these studies, this could mean that the studies did not have adequate power to detect reliably any difference in weight gain. This could also affect the reliability of this meta-analysis.

Questionable reliability of weight measures

Even among the 51 included studies that had reported weight gain, only some of these studies had objectively measured weight in a clinic. The others had either failed to report how weight was measured, or said that it was by people self-reporting their weight.

Study populations ‘unrepresentative’

Another important limitation is that, as most of the trials were looking at smoking-cessation treatments, the data was derived from people being treated for tobacco dependence in clinics. People who seek help to quit may differ from the general smoking population and may be more vulnerable to putting on weight, for a variety of reasons. As the authors suggested, most people do not attend smoking-cessation clinics or consult their doctor for help until they have tried and failed to stop smoking themselves, and it could be that people who are more dependent on smoking are more vulnerable to weight gain.

No data on quitters who relapsed

It is worth remembering that we do not know whether people who tried and failed to quit smoking experienced weight change. The authors of this review were specifically interested in weight change among people who successfully gave up and who did not receive treatment to help them quit. For this reason, the focus of their study was on weight change in “untreated quitters”. Although the researchers were primarily interested in those who quit without treatment, they did report weight change in the people in the “intervention” arms of the trial who were allocated to smoking-cessation treatments. These people experienced fairly comparable weight change to the untreated quitters.

Weight gain associated with smoking cessation is a topic of great significance in people’s battle to quit fags, as well as for public health policy-makers who want to encourage more people to quit. It is an area that clearly requires further research. However, the fact remains that for most people, the health benefits of giving up smoking far outweigh any modest temporary change in weight which may be associated with quitting. Giving up smoking may improve both appetite and sense of taste, so those who are trying to give up are advised to stick to healthy snacks such as fruit rather than fill up on crisps and biscuits, and to exercise regularly.

The best advice in the media coverage comes from a Department of Health spokesperson quoted on the BBC website: “The health benefits of quitting are well recognised[…] Getting support from nicotine replacement therapies or medication and the NHS Smokefree service can help in keeping down your weight.”

Analysis by Bazian
Edited by NHS Website

Links to the headlines

Ex-smokers 'gain more weight than thought'

BBC News, 11 July 2012

Links to the science

Aubin H, Farley A, Lycett D, et al.

Weight gain in smokers after quitting cigarettes: meta-analysis

British Medical Journal. Published online 10 July 2012